This invention relates to a rotary grinding mill and more particularly to a rotary grinding mill having a trunnion discharger which expels its discharge to a screen.
Grinding mills of the type herein considered are extremely large and often have what is called a "multiple pinion drive." A gear around the shell or trunnion extension is driven through a pinion(s) and possibly a speed reducer(s) by a motor(s) on each pinion drive train for the mill. With this type of arrangement the discharge of the trunnion is normally parallel with the axis of the mill and a single screen. However, one of the problems with a single discharge to a single screen is that the required screening capacity often cannot be obtained with a single screen. It has been proposed to use parallel double screens with the mill discharge divided by a splitter bar which would be adjustable to direct the material from the trunnion onto the dual parallel screens as may be desired. However, while this approach is a workable approach it has not been acceptable in most instances because of the experience industry has had with splitter bar arrangements in which they gradually become incrusted with a buildup of the material or slurry wear resulting in a gradual loss of adjusting capability.
The problem to be solved was to take the discharge of the mill (which is reversible in rotation) and split it evenly both volumewise and sizewise onto multiple vibrating screens. Thus, not only did the drive arrangement to the mill have to be reconsidered and redesigned, but the screens themselves had to be reoriented so that maximum advantage of available screen sizes could be obtained to handle the extremely large volume of mill discharge; with the division more or less of equal size and volume.